This invention relates to an assembly and a method for fastening a stent onto a catheter. This kind of device finds routine use in the area of percutaneous transluminal coronary angioplasty (PTCA) procedures, although it may be used in other types of procedures, as well.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Inflation expandable stents are well known and widely available in a variety of designs and configurations. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with the crimping of inflation expandable stents although self-expanding stent may be used as well.
An example of a stent is described in PCT Application NO. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
In advancing an inflation expandable balloon through a body vessel to the deployment site, the stent must be able to securely maintain its axial position on the delivery catheter, without trans-locating proximally or distally, and especially without becoming separated from the catheter. Stents that are not properly secured or retained to the catheter may slip and either be lost or be deployed in the wrong location or partially deployed. In securing a stent to a catheter, however, the stent must be crimped in such a way as to minimize or prevent altogether distortion of the stent and to thereby prevent abrasion and/or reduce trauma of the vessel walls.
In the past, crimping has been done by hand often resulting in the application of undesired uneven forces to the stent. Such a stent must either be discarded or re-crimped. Stents which have been crimped multiple times can suffer from fatigue and may be scored or otherwise marked which can cause thrombosis. A poorly crimped stent can also damage the underlying balloon.
Recently, stent crimping devices have been disclosed in U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085 to Timmermans et al., U.S. Pat. No. 5,626,604 to Cottone, Jr., U.S. Pat. No. 5,725,519, to Penner et al., U.S. Pat. No. 5,810,873 to Morales, WO 97/20593 and WO 98/19633.
All US patents and applications all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The present invention, in one embodiment, is directed to a stent crimper formed of an inner tube and an outer tube, the inner tube movably or slidably disposed in the outer tube. The inner tube has a first end and a slotted second end. The slotted second end comprises a plurality of flexible axially oriented fingers along the tube and is operable from an open configuration in which the fingers flare outward from the tube to a closed configuration. The inner diameter of the inner tube is sized to correspond approximately to the desired diameter of the crimped stent. The inner diameter of the outer tube is sized to substantially correspond to the outer diameter of the inner tube. In use, the fingers of the inner tube are opened, a stent, optionally disposed about a catheter, is placed therein and the outer tube slid over the slotted end of the inner tube.
In another embodiment similar to that described above, the inner diameter of the outer tube is greater than the outer diameter of the inner tube so that the outer surface of the inner tube and the inner surface of the outer tube are not in frictional engagement. The inner and outer tubes are, however, movably secured to one another. The device otherwise operates in the same way as the above described stent crimper. As the outer tube is slid over the slotted end of the inner tube, the fingers close down on the stent and crimp the stent. The stent will be crimped to a diameter approximately equal to the difference between the inner diameter of the outer tube and twice the wall thickness of the inner tube.
The invention is also directed to methods of crimping a stent as described above.
In yet another embodiment, the invention is directed to a stent crimper comprising a first support having an opening therethrough, the opening sized to allow a stent, optionally disposed about a catheter, therethrough and a second support, optionally having an opening therethrough both extending from a base. A plurality of flexible members extend between the first support and the second support. The members are disposed about the circumference of a circle everywhere along the length of the members. The flexible members extend through a bore in a movable die. In use, a stent, optionally disposed about a catheter, is placed in between the flexible members and passed through the bore in the die.
In yet another embodiment, the invention is directed to a method of crimping a stent to a stent delivery catheter using a pressure chamber. A stent disposed about a catheter is inserted in an elastomeric tube in a pressure chamber. The pressure chamber is pressurized collapsing the elastomeric tubing onto the stent and the stent onto the catheter.
In yet another embodiment of the invention, a sleeve is disposed about a stent mounted on a balloon. The balloon is inflated to a predetermined pressure. At the predetermined pressure, tension is applied to the sleeve and the balloon is allowed to deflate slowly. The application of tension to the tube causes the tube to stretch and the diameter to decrease thereby applying a crimping force to the stent. As a result of this method, some of the balloon folds will reside between struts of the stent. The sleeve may also be operated independently of the balloon in crimping the stent.
In another embodiment, the invention is directed to an apparatus and a method for crimping a stent by rolling the stent between two plates which are separated by a distance. The plates may be parallel to one another or disposed at an oblique angle relative to one another.
Another embodiment of the invention is directed to a stent crimper comprising a plurality of offset rotatable cams disposed about a center region. The center region is sized to contain a stent therein. Each cam is in mechanical communication with a cam rotating drive.
Another embodiment of the invention is directed to a stent crimper comprising a fixed roller and a plurality of translatable rollers which are translated, in sequence, to engage the stent and apply a crimping force thereto.